Everything in the lower is standard except the hammer spring. i would trade out the firing pins if it were here but it's still in springfield mass ......Update i called at 11:30 to Talk to a cust service supervisor. they stated she would call back no return call yet.....3 and a half hours tick tock tick tock.... must be busy.......

Update.... The day came and went no return call from the Cutsomer service Mgr/supervisor. This explains alot. Leadership and other things roll down hill. Monday I will be contacting her supervisor, someone in springfield mass has to be concerned about Smith and Wesson products and service...... will continue to update the thread as things move forward.........

I hope I never see that POS again but if i do i will go over it with a fine tooth comb. I hope they replace it/fix it etc so this thread can end on a semi positive note. The service and customer service depts failures and poor communication will echo for a long time in my mind and future purchase decisions. When i first dealt with the rep I told him the measure of a buisness is not whether a problem occurs but how it is handled when it does. This one has not been handled well.

Not to hijack thread but a few months ago I bought a Walther SP-22 from CDNN on close-out. I also bought a Walther pistol scope. Thought it would be cheaper to practice with than my .45 race gun. Anyway it wouldn't load after a couple of mags. Clean it and good for 20 rnds or so. I called Smith-Wesson who do Walthers work in the states. Talked to a real nice guy-I didn't have to be a Eddie Haskell with him-and he e-mailed a return shipping label to get it fixed. A couple weeks later I got a call and they said they couldn't fix it! Thet sent me a new P-22 and also took of the sights and sent me back the mags that were with the old pistol! Also paid my local gun shop for the transfer fee!! Now I need to find an old SP-22 to put the scope on or the fiber optics on. Or sell them. Any way they did me GREAT. Bill

It's good to hear there are good people in springfield mass, I always felt more comfortable with a large established company. I still hold hope for a positive resolution....but I'm not holding my breath. i can't quite fathom blaming a customer's lower for an issue with thier upper. seems like pass the buck to me. will post video and pics if they send the upper back unresolved.

Not that it is any help or consolation for your problem, but I purchased a S&W 5.45 upper three years ago. Probably 1,000 rounds down range. Never a stumble at all.
I shoot Bulgarian milsurp exclusively.
I put it on a standard DPMS lower and never even bothered with the heavy hammer spring as mine worked 100% out of the box. C-Products mags and all good.
Hope your problem resolves.

thanks to all for your suggestions encouragement and advice. You guys are they best of the best! Merry Christmas to all and may Santa bring all of you guns, ammo and mags a-plenty! I will update as things develop.

Well the customer disservice continues......I recieved a call from the customer service supervisor Kay ( or kate not sure she was eating while talking ) today. She stated there is nothing wrong with the upper they test fired it fuctioned flawlessly then snarkily stated it's made to fire only sammi approved ammo.She then snidely stated i should've sent the whole rifle. i tried to explain i wasn't given that option but she just kept talking and blaming my lower and defending the work in thier service dept. I must say she's good i amost started doubting my own experience with it. This experience has so soured me on the entire smith and wesson line and structure. so i tried to ask her if they had checked the headspace and she said of course they did....i told her to send it back at this point i didn't trust the service dept after not reading the letter and addressing a failure to feed issue when it was sent in for failure to fire. I will have a set of go nogo guages at the ready when it arrives and will video the headspacing and test firing if safe to do so and post it here. Will keep you all up to date as things continue to develop.